Electric heating element



ELECTRI G HEATING ELEMENT Filed June 28, 1959 INvENTDR. ASMLJND B.HCJL.AND.

BY M

v I ATT v.

Patented Oct. 5, 1943 ELECTRIC HEATING ELEMENT Asmund B. Holand, Westboro, Ontario, assignor of fifty per cent to Halvdan-J.

Canada, Eriksen,

Ottawa, Ontario, Canada Application June 28, 1939, Serial No. 281,667 Claims. (Cl. 201-67) This invention relates to electric heating elements and .more particularly to resistance heating elements for use in stoves, water-heaters and other electrically operated apparatus.

One of the objects of the present invention is to provide a device of this character which will enable the resistance element to obtain and maintain its embedded position in the insulation in spaced relation to the sheath or casing.

Another object of the invention is to provide a device of this character wherein the structure provides a single, waterproof casing for the unit.

A further object of the invention is to provide a device of this character in .which the casing or sheath may be shaped in curve, spiral, oval or other formations without disturbing the insulated position of the resistance element with respect to the casing.

A still further object of the invention is to provide a device of this character wherein a substantially solid yet yieldable wall of insulation envelopes the resistance element within the casing.

Yet a further object of the invention is to provide a device of this character which is simple in structure, rugged in nature and one that may be manufactured at a low cost.

Having regard to the foregoing and other objects and advantages which will become apparent as the description proceeds, the invention consists essentially in the novel combination and construction hereinafter described in detail and illustrated in the accompanying drawing in which:

Fig. 1 is a transverse section taken through a length of material for forming a casing or sheath with the longitudinal edges thereof down-turned, the material being ready for moulding to channel like formation.

Fig. 2 is a section of the material shown in Fig. 1 formed to open channel like formation.

Fig. 3 is a section of the channel with insulating material therein, the insulating material having been compacted to form a channel like bed in the insulation.

Fig.4 is a view similar to Fig. 3 showing an electric resistance element in position in the channel like bed of insulation with insulation added to fill the space within the confines of the resistance element.

Fig. 5 is a view showing insulating material added to completely envelope the electric resistance element with a trip of metal superimposed thereon, the strip of metal being shaped and the insulating material being compacted to form a relatively solid wall of insulation enveloping the electric resistance element.

Fig. 6 is a view of the completed unit shown in cross section and of substantially annular forma- Iii tion.

Fig. 7 is a view similar to Fig. 6 showing the unit shaped to substantially oval form in cross section.

Fig. 8 is a view of one end of a completed unit shown partly in elevation and partly in section.

Figs. 9 and 10 show modified forms of type structure.

Fig. 11 illustrates formed insulation including electric resistance element ready for insertion in a seamless tube.

Fig. 12 illustrates the completed unit shown in Fig. 11.

Fig. 13 shows formed insulation with a core removable for the insertion of the electric resistance element.

Referring now to the drawing wherein like numerals of reference designate corresponding parts in the several illustrations, the numeral l4 indicates a length of material of suitable proportions and thickness formed with down-turned longitudinal edges I5. This length of material may be of stainless steel, copper, iron or other metal and is pressed or died in a mould IE to form an open U shaped channel like formation I! as will be seen by reference to Fig. 2.

Into this channel like formation is introduced a quantity of compactible, preferablv granular, dry or dampened insulating material 18 such as magnesia, zirconia, silica or other appropriate compounds which will be compacted by suitable die means such as is indicated at I9 to form a channel like bed 20 in the insulation, preferably with curved shoulders 2]. Where the insulation material has been dampened prior to introduction, it permits the composition to be the more firmly and efllciently compacted so that in form it is of a substantially solid body or mass.

The insulating material having been compacted as above mentioned provides a channel body whose walls are of substantially even thickness. Into this channel of insulation an electric resistance element 22 is laid after which a quantity of insulation 23 such as silica is added to fill the spaces within the confines of the coils or spirals oi the resistance (see Fig. 4).

With the electric resistance element in position. a further quantity of dry or dampened insulating material is introduced into the channel to completely envelope the electric resistance element after which a metal strip or insert 24 is suable form is then brought into operation to shape the insert and compact the last introduced quantity of insulating material so that upon completing this last compacting operation I produce a longitudinal compacted mass 26 substantially annular in cross section with a relatively even thickness and density and an electric resistance element embedded centrally of a relatively solid wall which possesses yieldable properties (see Fig. 5). It will be observed here that the strip or insert, 24 isolates insulation from the extended legs of the channel enabling efficient sealing to be effected and at the same time the insert lends reinforcement to the structure. v

While I may refer to the die, mould, casing or sheath as substantially annular in cross section, it is not to be understood that this implies restriction since the formation may be annular, oval, triangular, square or other formation without departing from the scope or spirit of the invention.

In order to complete the forming of the casing or sheath, the channel forming sides 21 (see Fig. 5), are pressed inwardly and toward each other by suitable means after which they are welded, brazed or otherwise joined as at 28 to form a sealed casing which is provided with support means 29 (see Fi 6).

As is well known in the art, the article is subjected to heat treatment or baking to drive the moisture content from the insulating material. The customary terminals may be connected to the ends of the casing (see Fig. 8) either before or after baking and likewise the casing may be shaped either before or after heat treatment into curves, ovals, spirals or other appropriate or desired contours. Such shaping it will be observed by reference to Fig. 7, does not disturb the relative position of the electric resistance element due to the fact that such element is enveloped in a relatively solid yet yieldable insulating wall while the insulation within the confines of the resistance element are relatively less solid and consequently more readily yieldable. In the modified forms of structure shown in Figs. 9 and 10, it will be observed that the metallic strip or insert 24 is omitted and the open channel is closed by a plate 30 which may be welded, brazed or otherwise connected to the down-tumed edges l5.

What has just been described sets forth structure in which a casing is formed from a length of fiat metal in which an electric resistance element is embedded in insulation and sealed in a waterproof covering. It will be understood however that I do not wish to confine myself to this type of structure since, in practice, I have discovered that an electric resistance heating unit may be constructed employing seamless tubing rather than forming the casing from a length of flat metallic material. In this latter development, as observed in Fig. 11, it will be seen that apart from not employing the length of metal [4, the steps of introducing the insulating materials, the electric resistance element and the compactingare carried out in exactly the same manner as that already described. As exemplified in Fig. 11, a quantity of insulating material in dry or dampened form is introduced into the mould l6 direct where it is compacted to form the channel like bed in the insulating material. An electric resistance element is then placed in position in the channel of the insulation after which a quantity of insulating material is added to fill perimposed on the insulation. A die 25 of suitthe spaces within the confines of the resistance then a further quantity is introduced to envelope the resistance element. Compacting follows which forms the insulation into a relatively solid mass of substantially annular form in cross section as indicated at 3|. In this form the mass is compacted to a diameter slightly less than the internal diameter of the seamless tubing 32 which is adapted to envelope the mass. (See Fig. 11.) Further procedure from this point is the endwise insertion of the moulded mass into the seamless tubing 32 after which it is subjected to baking for dehydration of the insulation. Terminals maybe secured either before or after baking and the device is then ready for shaping into the required or desired curve, oval, spiral or other formation. In this particular type of unit the curves or spirals impressed thereon'will constrict the internal diameter of the seamless tubing so that notwithstanding a slight initial difference in the respective diameters of the mass and the tubing, such shaping will cause the insulating material to be firmly enveloped within the casing or tube 32 (see Fig. 12).

The modification illustrated in Fig. 13 shows the structure forming and compacting as already described. In this form however a core or tube 33 or other suitable means is inserted during the formation and is removed after formation to provide a centrally disposed opening in the insulation 3| for the insertion of the electric resistance element 22. The mass may be inserted in the seamless tubing either before or after the removal of the core 33. The removal of the core permits the introduction of the electric heating element after which a quantity of insulating material is added to fill the space within the confines of the resistance element.

The invention disclosed may be embodied in other specific forms without departing from the spirit or essential characteristics of the invention, the present disclosure is therefore to be considered in all respects as illustrative rather than restrictive and all changes coming within the meaning and range of equivalency of the claims are intended to be embraced therein.

What I claim as my invention is:

l. The method of producing an electric resistance heating unit comprising, forming a single length of sheet material into open channel like formation, introducing a quantity of relatively loose insulating material into the channel, com-' .pacting the said insulating material into a relatively solid body of channel like formation, inserting a resistance element in the channel of insulating material, introducing a further quantity of insulating material into the said channel sufficient to fill the spaces within the confines of the resistance element to form a core therein relatively less solid than the relatively solid body, introducing a still further quantity of insulating material into the channel like formation, inserting a metallic strip in the said channel and placing it upon the still further added quantity of insulating material, applying compacting pressure to the still further added quantity of insulating material to form a relatively solid wall of insulation around the resistance element, closing the channel forming length of material to envelope the insulating material and metallic strip to form a longitudinal casing, sealing the casing by welding its longitudinal marginal edges along the path of the metallic strip and shaping the casing to substantially oval form in cross section.

2. The method of producing an electric resistance heating unit comprising, forming a single length of sheet material with down-turned marginal edges into channel like formation, introducing a quantity of relatively loose insulating material into the channel, compacting the said insulating material into a relatively solid body of channel like formation, inserting a helical resistance element in the channel like formation of insulating material, introducing a further quantity of insulating material into the said channel sufiicient to fill the spaces within the confines of the resistance element to form a core therein relatively less solid than the relatively solid body, introducing a still further quantity of insulating material into the channel like formation, inserting a metallic strip in the channel and placing it upon the still further quantity of insulating material, applying compacting pressure to the metallic strip to compact the still further added quantity of insulating material to form a relatively solid wall of insulating material surrounding the resistance element, closing the channel forming length of material to envelope the insulating material and the metallic strip to form a longitudinal casing, sealing the down-turned marginal edges by welding and shaping the casing to substantially oval form in cross section.

3. An electric resistance heating unit comprising, a length of single-ply sheetmaterial shaped to longitudinal casing form substantially oval in cross section and having its longitudinal edges sealed by welding, an electric resistance element mounted within the casing, a relatively solid body of insulating material surrounding the electric resistance element having a core of relatively less solid insulating material within the confines of the electric resistance element and t a strip of metallic material disposed between the relatively solid body of insulating material and the inner wall of the casing along the path of the casing weld.

4. An electric resistance heating unit comprising, a length of single-ply sheet material having protruding marginal edges, the said edges being sealed by welding to provide a casing of longitudinal form substantially oval in cross section with a projecting supporting rib, a helical resistance element mounted within the casing, a relatively solid body of insulating material surrounding the resistance element having a core of relatively less solid insulating material with in the confines of the resistance element and a strip of metallic material disposed between the relatively solid body of insulating material and the inner wall of the casing along the path of the projecting supporting rib.

5. An electric resistance heating unit comprising, a length of single-ply sheet metal material having protruding marginal edges welded together to provide a casing of longitudinal form substantially oval in cross section with a pro- Jecting supporting rib extending longitudinally of the casing, a helical resistance element mounted within the casing, a relatively solid body of insulating material surrounding the resistance element having a core of relatively less solid insulating material within the confines of the resistance element.

ASMUND B. HOLAND. 

